1. Field of the Invention
This invention relates to the preparation of novel wax ester compounds wherein both the fatty acid and fatty alcohol moieties are vegetable oil derivatives. The compounds are useful lubricants and are particularly advantageous in the continuous casting of steel. They can also be sulfurized to yield extreme pressure and antiwear lubricant additives.
2. Description of the Prior Art
The continuous casting of steel is considered as one of the major technological advances in the steel industry in recent years. In conventional steelmaking, up to 30% of the steel poured is lost in ingot trimming and mill scale; continuous casting cuts these losses down to 10% or less. Continuous casting produces billets and slabs with no ingot pouring and reheating before rolling--processes required in the handling of blooms. Because of economic advantages there has been a continuous growth in this new steelmaking method. The capacity for continuous casting of steel in this country is about 40 million tons per year. Domestic steelmakers express the belief that eventually about half their production will roll off a continuous line. Based on the use of 4-6 ounces of lubricant per ton, a substantial market for lubricants for continuous casting of steel is developing.
The most important function of a mold lubricant is to prevent sticking. Without continuous and reliable lubrication of the mold walls, the steelmaking process slows down or stops. The most widely used lubricants to date have been rapeseed oil high in erucic acid and a blend of rapeseed oil with a more viscous mineral oil. Blown rapeseed is selected primarily because it does not penetrate into the surface of the steel. Crambe, another high erucic oil, in plant-scale tests by the steel industry, proved superior to rapeseed oil in continuous casting of steel. Other oils tried as lubricants are silicone, fish and mineral, as well as paraffin wax, inorganic salts, and mixtures of fatty acids and graphite [W. G. Ritter, Iron Steel Eng., Feb. 1967, pp. 113-118; and Nieschlag et al., JAOCS 48: 723-727 (1971)]. Mixtures of dimer and trimer of unsaturated fatty acids, a glyceride oil, and a mineral lubricating oil have also been reported, U.S. Pat. No. 3,640,860.
The properties which make the above compositions useful as lubricants in the continuous casting of steels are:
1. A viscosity of at least about 100 SUS at 100.degree. F.; PA1 2. a high flash point, at least about 500.degree. F. for forging grade steel; PA1 3. A high fire point; and PA1 4. A smoke point that is sufficiently high as to permit the steel mold interface to be visually observed. PA1 (1) CH.sub.3 (CH.sub.2).sub.x CH.dbd.CH(CH.sub.2).sub.y CH.dbd.CH(CH.sub.2).sub.z -- PA1 (2) CH.sub.3 (CH.sub.2).sub.x CH.dbd.CH(CH.sub.2).sub.y -- PA1 (3) CH.sub.2 .dbd.CH(CH.sub.2).sub.15 --; PA1 (4) ch.sub.3 (ch.sub.2).sub.16 --; and PA1 (5) CH.sub.3 (CH.sub.2).sub.14 --; PA1 (a) selectively reducing a first portion of the fatty acid mixture to substantially the corresponding alcohols; PA1 (b) esterifying a second portion of the fatty acid mixture with the alcohols obtained in step (a) in order to yield wax esters having the structural formula: ##STR1## where both R and R' are radicals independently selected from the group of radicals set forth above; and PA1 (c) recovering the wax esters for use as the lubricant composition.
U.S. Pat. Nos. 2,757,139, 3,130,159, 3,526,596, 3,620,290, and 3,915,872 disclose lubricant compositions comprising esters of fatty acids and alcohols. Most of these alcohols are derived from nonrenewable petrochemical sources and are in diminishing supply. Moreover, the compositions prepared therefrom have metalcasting lubricating properties inferior to rapeseed and crambe oils.
Also in the field of lubrication, there exists a need for synthetic extreme pressure (EP) and antiwear (AW) lubricant additives as replacements for the conventionally used sulfurized sperm oil (SSO). Extreme pressure additives prevent destructive metal-to-metal contact in lubrication at high pressure and/or temperature such as that found in certain gear elements in automotive vehicles and various industrial machines where high pressure can cause a film of lubricant to rupture. EP/AW lubricants should have good lubricity, good cooling properties, high film strength, good load bearing ability, and miscibility with the usual types of base oils. SSO satisfies these requirements and has been used extensively in EP/AW additives. However, in 1970, the United States placed the sperm whale on the endangered species list, and in 1971, banned the import of its products.
In U.S. Pat. No. 4,031,019, which is herein incorporated by reference, I disclose a class of lubricant alcohol esters prepared from free fatty acid mixtures obtained from selectively and partially hydrogenated soybean and linseed oils. These esters were characterized by lubricant properties superior to the prior art lubricants previously mentioned, and their sulfurized derivatives were shown to be at least comparable to SSO as EP/AW additives. The primary disadvantage of these esters is that the saturated alcohols used in their preparation are derived mostly from petrochemicals.
A preliminary attempt to synthesize wax esters from certain natural animal and vegetable oils for use as possible sperm oil replacements was disclosed in Perlstein et al., JAOCS 51: 335-339 (Aug. 1974). The somewhat complicated method involved a Bouveault-Blanc reduction of triglycerides to sodium alkoxides which were decomposed with urea and then esterified with the triglycerides. The properties of the products were never reported and the compositions have not attained the status of sperm oil replacements.